ABSTRACT Small cell lung cancer (SCLC) is particularly aggressive, and characterized by rapid growth and early metastasis. At present, there is no data concerning SCLC two-dimensional polyacrylamide gel electrophoresis (2-DE) reference map,and its protein profiles in public databases. This study was to establish a well-resolved, reproducible 2-DE map of proteome in SCLC cell line NCI-H446, and analyze its protein profiles.
Two-DE was applied to separate the total proteins of NCI-H446 cells, which were then silver-stained in the gel. Well-separated protein spots were selected from the gel by ImageMaster 2D analysis system. Matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF-MS), peptide map fingerprinting (PMF),and database searching were used to identify the protein spots.
Clear,well-resolved, reproducible 2-DE patterns of proteome in NCI-H446 cells were obtained. The average protein spots of 3 gels were 1506+/-74; and 1412+/-56 spots were matched with an average matching rate of 93.4%. The average deviation of spot position was (0.96+/-0.27) mm in IEF direction, and (1.24+/-0.41) mm in SDS-PAGE direction indicating relatively good reproducibility of the protein spots. Fifty-eight proteins were identified, certain proteins were products of oncogenes, and others were involved in cell cycle regulation, and signal transduction.
A reference map of NCI-H446 cells was established,certain proteins were identified by MALDI-TOF-MS and PMF. These data will be useful for establishing human SCLC proteome database.

[Show abstract][Hide abstract]ABSTRACT: To identify potential markers associated with non-small cell lung cancer (NSCLC) metastasis to brain, comparative proteome analysis on two lung squamous cell carcinoma (SCC) cell lines, NCI-H226 and H226Br (the brain metastatic cell line of NCI-H226), was performed using two-dimensional electrophoresis (2-DE) followed by a tandem mass spectrometer with a matrix-assisted laser desorption/ionization (MALDI) source. Twenty differential proteins were identified, of which 6 proteins were up-regulated in H226Br cell compared with NCI-H226 cells, whereas 14 proteins were down-regulated. S100A7 and 14-3-3sigma, two of candidate proteins significantly upregulated and downregulated in H226Br cell, were selected to verify the liability of the differential proteins by Western blot. The results were in accordance with 2-D data. To determine whether S100A7 overexpression is actually associated with SCC metastasis to brain, S100A7 protein was testified in 10 brain metastasis tissues from NSCLC, 38 primary NSCLC tissues including half matched local positive lymph nodes, 5 primary brain tumors and 2 non-cancer brain tissues by immunohistochemistry. Of particular interest to us was that the positive staining of S100A7 could be found in 3/5 (60%) brain metastases tissue from SCC and 8/21 (38%) the primary lung SCC tissues, while no positive staining was observed in the brain metastases tissue from Ad (n=5), the primary adenocarcinoma (Ad) tissues (n=17), the primary brain tumors (n=5), all local positive lymph nodes from the primary NSCLC (n=19) and non-cancer brain tissues (n=2). These findings suggest that S100A7 expression is closely associated with SCC metastasis to brain and may be a potential biomarker for monitoring the development of SCC.

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